1. Field of the Invention
The invention relates generally to piston rings for internal combustion engines, and more particularly to coated piston rings, and methods of forming the coated piston rings.
2. Related Art
A piston of a reciprocating engine, such as an internal combustion engine, typically includes rings disposed in grooves along the outer diameter of the piston. The piston rings facilitate guiding of the piston during reciprocation in a cylinder bore. The piston rings also seal combustion gases and inhibit the upward passage of oil. The piston rings are subject to wear as they move along the cylinder bore due to gas load and their own inherent load. Accordingly, the piston rings are typically coated or treated to enhance wear resistance. For example, the piston rings may be nitrided, coated with chromium, or coated with a ceramic, which may be applied by physical vapor deposition (PVD).